JOINING EFFICIENCY OF SUPERPLASTIC 8090 Al-Li THIN SHEETS USING ELECTRON OR LASER BEAM WELDING

Systematic characterization of the electron and laser beam welding (EBW and LBW) behavior of superplastic graded 8090 Al-Li thin sheet has been made, including both autogenous bead-on-plate and overlap welds. The basic relationships between fusion zone characteristics and post-weld properties versus welding parameters were established. The porosity formed during EBW was resulted from the hydrogen enriched surface layer, coupled with minor effect from Li and Mg evaporation, while under LBW was due to collapsed central key-holes. Lap-shear strengths of as-welded (AW) and AW+T6 specimens were scattered within 110-180 MPa and 170-220 MPa, respectively, with a joint efficiency 70-85%. T-peel strengths were 30-55 N/mm for the AW samples and 20-75 N/mm for the AW+T6 joints, similar to those reported for diffusion bonded joints.